Primitive Classes

Primitive classes define nominal value types.

They are used for branded primitives, units, and small value-shaped aggregates. Primitive classes live in a separate type universe from reference classes. A primitive class cannot inherit from a reference class, and a reference class cannot inherit from a primitive class.

The editor renders the 🪨 unicode character before a primitive class definition when one is detected.

🪨 UserId is u64 (
)

Primitive classes are immutable values. They do not have object identity, are not reference counted, and do not support ghosts.

Bases

A root primitive class may use one of three base forms:

primitive
a concrete primitive, such as u64, string, f32, or boolean
a primitive group, such as AnyInteger, AnySignedInteger, or AnyNumeric

Primitive classes also support single inheritance from another primitive class. They do not support multiple inheritance. A primitive class chooses one base.

The provisional numeric annotation is not a primitive class base. To define a primitive class over a family of number types, use a primitive group instead.

Concrete Primitive Bases

Inheriting from a concrete primitive creates a branded primitive with the same underlying representation.

🪨 UserId is u64 (
)

id = UserId(123)

UserId is a distinct nominal type, but its stored value is a u64.

Primitive classes based on a concrete primitive receive an implicit first construction parameter. The parameter is compatible with the base primitive. The editor may show this parameter in the function signature, but it does not appear in the underlying text file.

🪨 BracketedString is string (
)

value = BracketedString("hello")

Primitive class chains rooted in a concrete primitive cannot declare stored fields. Once the chain has chosen a concrete primitive representation, its shape is fixed.

🪨 UserId is u64 (
	label is string // ❌ compiler notice
)

Primitive Group Bases

Inheriting from a primitive group creates a parametric primitive class over the concrete primitives in that group.

🪨 DatabaseId is AnyUnsignedInteger (
)

id = DatabaseId(123)

AnyUnsignedInteger is not ordinary inheritance. It is a constrained provisional base. The concrete representation follows the same provisional number rules used elsewhere in the language, but it is constrained to the primitive types in the group.

Primitive group bases also receive an implicit first construction parameter. The parameter is compatible with the group.

Primitive class chains rooted in primitive groups cannot declare stored fields.

Fresh Primitive Shapes

Inheriting directly from primitive creates a fresh primitive shape.

🪨 Point is primitive (
	x is f32
	y is f32
)

Fields are allowed only for primitive class chains rooted at primitive.

Aggregate primitive classes may contain primitive fields and reference fields.

🪨 LabeledPoint is primitive (
	x is f32
	y is f32
	label is string
	owner is User
)

The primitive class itself is still a value. If it contains a reference field, that field is a reference value stored inside the primitive value.

Primitive classes based directly on primitive do not receive an implicit first construction parameter, because there is no single base representation to pass in.

Primitive Class Inheritance

A primitive class may inherit from one other primitive class.

🪨 Vector2 is primitive (
	x is f32
	y is f32
)

🪨 Vector3 is Vector2 (
	z is f32
)

The root of the primitive class chain determines its representation family.

If the chain is rooted at primitive, descendants may add stored fields.

🪨 Vector4 is Vector3 (
	w is f32
)

If the chain is rooted at a concrete primitive or primitive group, descendants keep the same scalar representation family and cannot add stored fields.

🪨 UserId is u64 (
)

🪨 AdminUserId is UserId (
)

Primitive class inheritance creates nominal compatibility and an ancestor view. A value accessed through an ancestor type shows the ancestor's member and field surface.

v is Vector2 = Vector3(1, 2, 3)

v.x
v.y
v.z // ❌ compiler notice

The descendant view can be restored with an attestation. If the attestation fails, the access path short-circuits.

zValue = (v is Vector3).z
console.log(zValue) // f32 or null if the attestation fails

Constructors

Primitive classes may define constructors.

For concrete primitive and primitive group bases, construction begins with the implicit first parameter. Inside the constructor, this refers to the current primitive class value.

A constructor may call super(value) to replace the underlying base value for the value being constructed.

🪨 BracketedString is string (
	constructor() (
		super("[" + this + "]")
	)
)

value = BracketedString("hi")
console.log(value) // "[hi]"

The value passed to super(...) must be compatible with the base primitive or primitive group. If the constructor does not call super(...), the original implicit value is used.

For primitive classes based directly on primitive, there is no base value to replace, so super(...) is not available.

🪨 Point is primitive (
	x is f32
	y is f32
	
	constructor(x is f32, y is f32) (
		this.x = x
		this.y = y
	)
)

Constructors do not return values.

Members

Primitive classes may define functions, getters, static members, and operator overloads.

🪨 Counter is u64 (
	next() is Counter (
		return Counter(this + 1)
	)
)

Primitive classes cannot define setters or ghosts.

Functions on primitive classes do not mutate the existing value. They return new values when a changed value is needed.

Shadowing

A primitive class can define a member with the same name as a member available on its base. This shadows the base member for the primitive class.

There is no virtual dispatch. Member lookup is selected by the static type of the value.

When a shadowing member needs to call the base behavior, it can use super.

🪨 MyString is string (
	toString() is string (
		return "MyString(" + super.toString() + ")"
	)
)

For ordinary operations, use this.

🪨 Score is int (
	add(amount is int) is Score (
		return Score(this + amount)
	)
)

Equality

Typical has strict equality and loose equality.

Strict equality requires the primitive class and the underlying value to match.

Loose equality compares the underlying data. Branded primitive types may be different.

🪨 UserId is u64 (
)

🪨 OrderId is u64 (
)

user = UserId(10)
order = OrderId(10)

user === order // false
user == order // true

For numeric primitive classes with different concrete numeric representations, loose equality follows the normal numeric conversion rules.

Units

A numeric-backed primitive class marked with declare unit can be used as a unit suffix.

📏 cm is AnyNumeric (
	declare unit
)

width = 10cm

Unit syntax and unit operator behavior are described in 04-Units.

Operator Overloads

Operator overloads are supported only for primitive classes.

They may be defined inside a primitive class.

🪨 Point is primitive (
	x is f32
	y is f32
	
	+ (other is Point) is Point (
		return Point(this.x + other.x, this.y + other.y)
	)
)

They may also be defined inside an extension class, but only when the extension class targets a primitive class.

🔌 PointOperators is extension of Point (
	- (other is Point) is Point (
		return Point(this.x - other.x, this.y - other.y)
	)
)

(Note that primitive classes are required in order to overload operators as the feature is not supported for reference classes)